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Geotechnical Engineers& <br /> 17 March 1995 Environmental Consultants <br /> File No. 20200-002 <br /> Division of Minerals and Geology <br /> Department of Natural Resources <br /> 1313 Sherman St., Room 215 <br /> Denver, CO 80203 <br /> Attention: Mr. Carl B. Mount <br /> Subject: Cooley Grav any - Morrison Quarry `a <br /> Permit . M-73-021 - 1994 Annual Report rn <br /> r~ <br /> in c'n GW <br /> Dear Mr. Mount: <br /> rn� <br /> o <br /> INTRODUCTION <br /> cr•+ <br /> On behalf of Cooley Gravel Company (Cooley), Haley & Aldrich is pleased to submit this geotechnical <br /> addendum to the 1994 Notice of Intent to Continue Mining Operations/Annual Report for the subject <br /> Regular (112) Mining and Reclamation Permit. Cooley submitted their Annual Report form and annual <br /> fee on 28 December 1994. this addendum is required to provide supplemental geotechnical data and <br /> evaluations to comply with the conditional approval of permit Amendments No. 3 and No. 4. These <br /> Amendments describe in detail The Observational Method approach to mine slope design being <br /> implemented at the quarry whereby conservatively designed slope angles may be modified to steeper <br /> configurations based on ongoing collection of rock mass property data and updated slope stability <br /> evaluations. Specifically, this letter report provides supplemental data required by the Division of <br /> Minerals and Geology (DMG) per Stipulation No. 4 in your letter of Conditional Approval of <br /> Amendment No. 4, dated 16 February 1995. <br /> BACKGROUND <br /> Mine plan Amendment No.3 revised earlier mine plans for the Central Quarry area only. The significant <br /> changes presented in this amendment were a reconfiguration of the East Highwall to address slope <br /> instabilities in that area, and the provisional change in slope inclinations elsewhere to as steep as <br /> 0.5H:1V. Steeper slope inclinations were based on changing from an 80 ft bench and 80 ft highwall <br /> configuration to a 40 ft bench and 80 ft highwall configuration. As a condition of the amendment, the <br /> steeper slopes and revised configuration could be implemented only in accordance with specific <br /> predetermined steps outlined in the Observational Method. Additionally,the amendment required annual <br /> reporting of the geotechnical data, slope stability evaluations, and current mine conditions in areas where <br /> steeper slopes were utilized. These requirements are applicable only in areas where the slope <br /> configuration is more aggressive than the 80 ft bench and 80 ft highwall configuration. <br /> RP08267.200 1 <br /> 1600 Broadway <br /> Suite 1125 <br /> Denver,CO 80202 Offices Scarborough,Maine Rochester,New York <br /> Tel:303/832-9636 Cambridge,Massachusetts Silver Spring,Maryland Cleveland,Ohio <br /> Fax:303/832-9616 Glastonbury,Connecticut Bedford,New Hampshire <br />